BIOTREATMENT OF SURFACE WATERS TO REMOVE PESTICIDES
Report No FR/K0001
- Members of FWR expressed concern about the contamination of
source waters by triazine herbicides and the difficulties of
ensuring their removal in water treatment to the levels required by
legislation on drinking water quality.
- FWR, therefore, commissioned the Biological Laboratory,
University of Kent, to investigate the potential for microbiological
degradation of the two most common triazine herbicides, atrazine and
simazine. The contract, initially for two years from November 1990,
has been funded outside the core programme from FWR's investment
- This interim report gives some background information, summarises
the progress to date, and describes the pilot-scale studies planned
to start in summer 1992.
- Bacteria have been isolated from various sources which can
utilise atrazine and/or simazine (at 10mg/l) as a source of carbon
and nitrogen. Not all isolates could degrade both herbicides, and
some isolates were more effective at 10ºC than at 30ºC. The extent
and rate of degradation (from an initial concentration of 1µg/l),
using the most promising isolates , were both inadequate for
application to water treatment.
- Indications, to date, are that the removal of triazines is much
improved in the presence of GAC and appropriate bacterial cultures.
The carbon provides a physical support for the bacteria, which then
develop an active biofilm that effectively concentrates the
herbicides by adsorption and absorption. This provides elevated
substrate concentrations for bacterial growth.
- Bench-scale experiments are in progress to define the behaviour
of the biofilm in GAC packed beds and to measure herbicide
degradation at different influent concentrations and retention
- Results will be used to design a series of pilot-scale
experiments, to begin in mid 1992, operating on a 15-minute contact
time. The effect of herbicide concentration, background water
quality and inoculant establishment will be examined.
Copies of the Report are available from FWR, price £15.00 less 20% to FWR Members